The capacity of a two-stage compressor is a function of the volumetric efficiency, V.sub.e, the change in enthalpy .DELTA.H, and the displacement efficiency, D.sub.e. In two-stage reciprocating compressor systems the cylinders are divided between the two stages with the first stage having, typically, twice as many cylinders as the second stage. Unloading of this arrangement is normally achieved by hot gas bypass or suction cutoff of one or more cylinders of the first stage. In fact, the entire first stage can be unloaded so that the second stage is doing all of the pumping and is being supplied at the compressor suction pressure. Since the entire first stage discharge may be bypassed to suction, this arrangement also serves to negate the capacity increase associated with the use of an economizer.